The present invention relates to a bicycle frame incorporating an easily manufactured and easily replaceable shock absorber mechanism that provides increased torsional resistance.
Applicant's prior U.S. Pat. Nos. 4,792,150, 4,669,747, and 5,080,384, which are incorporated by reference, disclose a new type of bicycle frame incorporating a leaf spring connection between the top crossbar and seat tube (center post) of the frame, with a flexible cable connector extending between the head tube and lower end of the seat tube. The spring employed in U.S. Pat. Nos. 4,792,150 and 5,080,384 is a leaf spring comprising an elongated laminated fiberglass bar or plate having rounded edges that fit closely in oval openings in opposed fittings on the crossbar and seat tube. The springs are formed in multiple laminations of fiberglass reinforced resins. A substantial amount of work is required to shape the spring plates so that they fit closely in the fittings in the crossbar and seat tube. In addition, the spring plates have to be securely held in place by epoxy in order to maximize the rigidity of the frame. All of this requires a considerable amount of handwork and expense.
During operation over an extended period of time, all spring members eventually wear out. This is true of the fiberglass spring shown in the referenced patents. When this occurs, because of the complex construction of the springs and the extensive handwork required to remove and install new springs, springs generally are not replaced in the field. Instead, the frame must be returned to the factory for installation of new springs. This involves considerable expense to the bicycle owner and a considerable delay in the use of the bicycle.
An object of the present invention is to provide a suspension frame employing rod-shaped springs that provide increased torsional rigidity and yet are less expensive and are easily replaceable by the bicycle owner in the field. Other objectives of the present invention are to incorporate the new spring mechanism in a special collapsible or folding frame and to provide for wire management through a new wire management tube.